Purpose :
Numerous studies in healthy subjects have demonstrated that central corneal thickness (CCT) is thicker when measured with ultrasound pachymetry compared to optical pachymetry. The aim of this study was to evaluate to which extent these findings may be valid for glaucoma patients.

Methods :
41 glaucoma patients (69 eyes) as well as 32 age-matched (51 eyes) and 25 younger controls (50 eyes) were included in this prospective comparative study. CCT measurements were performed using the following techniques: ultrasound pachymetry (UP, Pachy Meter SP 3000, TOMEY), noncontact specular microscopy (SM, CEM-530 NIDEK Specular Microscope) and the Pentacam Scheimpflug technique (PC, OCULUS Pentacam® HR 70900).A linear mixed model with repeated measures was used to determine whether the mean values of CCT measured with the three types of measurement technique differed significantly. The inclusion of both eyes of some individuals were considered as a random factor in the model. The level of concordance was assessed using Bland–Altman plots.

Conclusions :
The study verifies that ultrasound pachymeters measure CCT thicker than optical pachymeters in young healthy subjects. This difference between UP and SM is no longer observed in age-matched subjects and is even reversed in glaucoma patients. CCT in glaucoma patients is generally thinner than in healthy subjects, without significant differences between the measurement techniques. This could be explained by a higher ultrasound velocity of the cornea in glaucoma patients.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.